The following code fails:

    >>> lcls = {'w': 100}
    >>> eval('[w for x in ("hello", "world")]', None, lcls)
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
      File "<string>", line 1, in <module>
      File "<string>", line 1, in <listcomp>
    NameError: name 'w' is not defined
    >>> eval('[w, w, w]', None, lcls)
    [100, 100, 100]

whereas in python2 it succeeds

    >>> lcls = {'w': 100}
    >>> eval('[w for x in ("hello", "world")]', None, lcls)
    [100, 100]